JP6088722B1 - Thermostatic bath electronics - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermostat crystal oscillation device capable of maintaining a constant temperature of a crystal resonator housed in a thermostat bath and ensuring a stable operation of the crystal resonator. SOLUTION: A measured temperature Tic based on an outside air temperature 4 measured by a temperature sensor 2 is compared with a set temperature Tr, and is stored in a constant temperature bath 100 controlled so as to reduce the difference between the two. Is a thermostat crystal oscillation device having a control system 101 for controlling the temperature of the quartz crystal resonator 3 that is affected by the environmental temperature to a target temperature Ttarg that is a predetermined fixed value. When the temperature Tic is decreasing, the set temperature Tr is increased, and when the measured temperature Tic is increasing, the set temperature Tr is decreased. δT is added to generate a new set temperature Tr to be compared with the measured temperature Tic. [Selection] Figure 1

Description

  The present invention relates to a thermostatic bath type electronic apparatus, and is useful when applied to a thermostatic bath crystal oscillator.

  Crystal oscillators applied to crystal oscillators have the property that the characteristics of oscillation frequency with respect to temperature fluctuate greatly, and various techniques are used to compensate for this and ensure high-accuracy and stable frequency characteristics. Has been proposed. A conventionally known thermostatic chamber type crystal oscillation device (hereinafter referred to as OCXO) is one type (see, for example, Patent Document 1).

  This type of OCXO is stored in a thermostatic chamber that is a housing by comparing the measured temperature related to the outside temperature measured by the temperature sensor with the set temperature and controlling the heat source so that the difference between the two is reduced. The temperature of the quartz crystal resonator is held at a predetermined target temperature. More specifically, normally, a temperature sensor, a temperature setting unit where a predetermined target temperature is set, a comparator, a control means such as a transistor, a heater as a heat source, and the like are integrated together with an oscillation circuit that drives a crystal resonator. It is modularized, and the module is housed in a thermostat together with a crystal resonator.

  In such OCXO, the temperature in the module is mainly measured by a heater or the like based on the temperature detected by the temperature sensor due to the distance between the temperature sensor that detects the temperature in the module and the crystal oscillator. Even when the target temperature is controlled to a predetermined set temperature, a divergence occurs between the set temperature and the temperature of the crystal resonator that defines the oscillation frequency. This is because the temperature of the crystal resonator depends on various factors such as heat leakage from the thermostat.

  As described above, in the OCXO according to the related art, heat leakage from the thermostatic chamber is inevitably caused, so that it is difficult to keep the crystal resonator at a constant temperature. For this reason, it becomes a cause of fluctuation of the oscillation frequency.

  Therefore, in the OCXO according to Patent Document 1, a temperature signal output from a temperature sensor that detects the temperature in the module is taken into the arithmetic processing unit in order to control the amount of heat generated by the heater. Then, a predetermined calculation is performed on the basis of the internal temperature signal by the calculation processing unit using a correction function for each OCXO obtained in advance, and a correction signal representing the correction amount of the oscillation frequency is obtained. Based on this correction signal, for example, the control voltage of the voltage controlled crystal oscillator (VCXO) is controlled to correct the oscillation frequency. That is, the OCXO disclosed in Patent Document 1 employs OCXO as a basic structure and applies the concept of temperature compensation (TC) to obtain a stable and highly accurate oscillation frequency over a wide temperature range even when the ambient temperature changes. Devised to be able to. Conventional technology that uses OCXO as the basic structure and devised to obtain a stable and accurate oscillation frequency over a wide temperature range even if the ambient temperature changes by applying the concept of temperature compensation (TC) In addition, there are Patent Document 2 and Patent Document 3.

US Pat. No. 7,573,345 US Patent Publication No. 2003/0197567 JP 2010-213102 A

  The OCXOs described in Patent Documents 1 to 3 apply the concept of temperature compensation (TC) on the premise that it is impossible to make the temperature change of the crystal resonators they have constant. That is, by combining the concept of TC with OCXO, a stable and highly accurate oscillation frequency can be obtained over a wide temperature range even if the ambient temperature changes. For this reason, the new subject that the structure for compensation becomes complicated arises.

  For example, in the OCXO disclosed in Patent Document 1, in combination with the fact that the temperature characteristic of the oscillation frequency of the crystal resonator becomes nonlinear, a plurality of measurements of the ambient temperature are required to create a correction function for temperature compensation. It is necessary to detect the oscillation frequency for each OCXO at the point. Therefore, the creation of this correction function is troublesome.

  Such a problem also exists in Patent Document 2 and Patent Document 3 in which TC is performed under the premise that it is impossible to make the temperature change of the crystal resonator constant. This is because it is necessary to generate a correction function for performing temperature correction of the oscillation frequency of the crystal resonator whose temperature characteristics are nonlinear.

  In view of the above-described problems of the prior art, the present invention greatly varies in characteristics with respect to temperature, such as a crystal resonator housed in a thermostat, even when heat leaks from the thermostat to the outside air. An object of the present invention is to provide a thermostatic bath type electronic apparatus that can maintain a constant temperature of a device and guarantee a stable operation of the device.

  The present invention is based on new knowledge obtained by analyzing the relationship between the flow of thermal energy and the temperature of each part in a conventional OCXO. First, the analysis result and new knowledge based on the analysis result will be described. Here, first, the contents of symbols used in the following description are defined.

<Definition of symbols>
Here, first, the contents of symbols used in the following description are defined.
Setting temperature: Tr
Heat source (heater) temperature: Tht
Measured temperature by temperature sensor (circuit temperature in IC based on outside air temperature): Tic
Temperature of the crystal unit in the thermostatic chamber: Tx
External temperature of the temperature chamber (outside temperature): Tout
Quartz crystal target temperature (target): Ttarg
Circuit gain: B
The amount of heat generated by the heat source (power consumption): P
Thermal resistance between the heat source and the outside of the temperature chamber: Θho
Thermal resistance between heat source and temperature sensor: Θhc
Thermal resistance between the heat source and the crystal unit: Θhx
Thermal resistance between the temperature sensor and the outside of the temperature chamber: Θco
Thermal resistance between the crystal unit and the outside of the thermostatic chamber: Θxo
Module coefficient (constant) determined by thermal resistance between components when mounting components: M (Mht, Mic, Mx)

<The flow of thermal energy in OCXO>
FIG. 3 is a schematic diagram illustrating the relationship between the flow of thermal energy and the temperature of each part in OCXO. As shown in the figure, the heat generated by the heat source 1 usually formed by a heater is transmitted to the temperature sensor 2 based on the thermal resistance Θhc, to the crystal resonator 3 based on the thermal resistance Θhx, and further to the thermal resistance Θho. Each part leaks to the outside air 4 outside the thermostat 100, and each part is heated. At the same time, the outside air 4 is heated by heat leaking from the temperature sensor 2 based on the thermal resistance Θco, and from the quartz oscillator 3 by heat leaking from the thermostat 100 based on the thermal resistance Θxo.

<Relationship of temperature when outside temperature is constant>
First, the relationship of the temperature of each part when the outside air temperature 4 becomes constant and becomes an equilibrium state will be considered.

At this time, since the amount of heat generated by the heat source 1 (temperature Tht) and the total amount of heat leaked from the heat source 1 to the outside air 4 are balanced, the following relationship is established.
P = (Tht-Tout) / Θho
Solve the above equation for Tht to obtain the following equation.
Tht = P ・ Θho + Tout (1)
Here, when the thermal resistance Θho is defined as a constant relating to the heat source 1 as a module coefficient Mht, the above equation (1) is expressed by the following equation (2).
Tht = P ・ Mht + Tout (2)

  In this case, since the outside air temperature Tout is in an equilibrium state, the outside air temperature Tout is a constant, and the generated heat amount P is also a constant here. That is, the temperature Tht of the heat source (heater) 1 is a linear function with respect to the module coefficient M (M = Mht) where the constant amount of heat P is a slope and the constant outside air temperature Tout is a y-intercept.

Next, since the amount of heat received by the circuit from the heat source 1, that is, the amount of heat received by the temperature sensor 2, and the amount of heat flowing from the temperature sensor 2 to the outside air 4 are balanced, the following relationship is established.
(Tht-Tic) / Θhc = (Tic-Tout) / Θco

Here, if the measured temperature Tic is solved by substituting the temperature Tht of the heat source 1 in the equation (1), the following equation is obtained.
Tic = Tout + P ・ Θho ・ Θco / (Θhc + Θco)

Here, when the module coefficient is defined as Mic = Θho · Θco / (Θhc + Θco), the following equation is obtained.
Tic = P ・ Mic + Tout (3)

  Equation (3) shows the module coefficient M (= Mic) in which the measured temperature Tic is a constant, the amount of heat P being a slope, and the outside temperature Tout being a constant is the y-intercept, as in the case of Equation (2). It shows that it becomes a linear function.

Similarly, the temperature Tx of the crystal resonator 3 can be expressed by the following equation.
Tx = Tout + P ・ Θho ・ Θxo / (Θhx + Θxo)

Here, if defined as Mx = Θho · Θxo / (Θhx + Θxo), the temperature Tx of the crystal unit 3 is expressed by the following equation (4).
Tx = P ・ Mx + Tout (4)

  According to the above equation (4), the temperature Tx of the crystal unit 3 is also a linear function with respect to the module coefficient M (= Mx), where the constant amount of heat P is the slope and the constant outside air temperature Tout is the y-intercept. It has become.

  FIG. 4 shows the relationship between the module coefficient M and the temperatures Tht, Tic and Tx as described above. In FIG. 4, the magnitude relationship of the module coefficient M is depicted as Mx <Mic <Mht in FIG. 4, but the magnitude relationship depends on the arrangement of component parts of the OCXO. change. However, there is no difference in that everything is basically expressed by a linear function relationship.

<Relationship of temperature when outside temperature fluctuates>
Next, a general OCXO circuit operation when the outside air temperature Tout varies will be considered. The OCXO detects a temperature difference between the set temperature Tr and the actually measured temperature Tic detected by the temperature sensor 2 and supplies a current that reduces the temperature difference to the heat source (heater) 1, so that the inside of the thermostatic chamber 100. The temperature is kept constant.

Here, assuming an operation under a constant power supply voltage, the electric power as thermal energy is expressed by V · I. Therefore, keeping the temperature in the thermostatic bath 100 constant means that the set temperature Tr and the measured value are measured. It is synonymous with generating electric power proportional to the temperature difference (Tr-Tic) of temperature Tic. That is, a predetermined amount of power is consumed to generate a heat quantity P expressed by the following equation (5).
P = B ・ (Tr-Tic) (5)

By substituting the relationship of equation (5) into equation (3), the following equation is obtained.
Tic = B ・ Mic ・ (Tr-Tic) + Tout

The following formula is obtained by subtracting the sides of the above formula from the set temperature Tr.
Tr-Tic = -B ・ Mic ・ (Tr-Tic) + Tr-Tout
The above equation is solved for Tr-Tic to obtain the following equation (6).
Tr-Tic = {1 / (1 + Mic ・ B)} ・ (Tr-Tout) ... (6)

The following equation (7) is obtained by modifying the above equation (6).
Tic =-{1 / (1 + Mic ・ B)} ・ (Tr-Tout) + Tr (7)

  Referring to the above equation (7), the difference between the set temperature Tr and the measured temperature Tic of the temperature sensor 2 is proportional via a proportional constant {1 / (1−Mic · B)}.

  That is, as shown in FIG. 5, the measured temperature Tic represented by the equation (7) is Tr having an inclination − {1 / (1 + Mic · B)} with the set value Tr being a constant as an intercept. -Linear function for Tout.

On the other hand, the difference (Tic−Tx) between the actually measured temperature Tic of the temperature sensor 2 and the temperature Tx of the crystal unit 3 can be expressed by the following equation from the equations (3) and (4).
Tic-Tx = P ・ (Mic-Mx)
Substituting equation (5) into the above equation and solving for temperature Tx yields:
Tx = Tic-B ・ (Mic-Mx) ・ (Tr-Tic)
Furthermore, the following equation is obtained by arranging the above equation from the set temperature Tr.
Tr-Tx = {1 + B ・ (Mic-Mx)} ・ (Tr-Tic)
Furthermore, the following equation (8) is obtained by substituting equation (6) into the above equation.
Tr-Tx = {1 + B ・ (Mic-Mx)} ・ {1 / (1 + Mic ・ B)} ・ (Tr-Tout) ... (8)

The following equation (9) is finally obtained by modifying the above equation (8).
Tx =-{1 + B ・ (Mic-Mx)} ・ {1 / (1 + Mic ・ B)} ・ (Tr-Tout) + Tr (9)

  In the above equation (9), the temperature difference between the set temperature Tr and the temperature Tx of the crystal unit 3 is also a proportional constant of {1 + B · (Mic-Mx)} · {1 / (1 + Mic · B)}. It is shown that it is proportional to the temperature difference (Tr-Tout) between the set temperature Tr and the outside air temperature Tout.

  That is, as shown in FIG. 5, the temperature Tx of the crystal unit 2 represented by the equation (9) has an inclination − {1 + B · (Mic−Mx)} · It is a linear function for Tr-Tout with {1 / (1 + Mic · B)}.

  In the case shown in FIG. 5, the inclination of the temperature Tx of the crystal unit 3 is drawn so as to be larger than the actually measured temperature Tic of the temperature sensor 2, but these magnitude relationships are related to the component layout design of the OCXO module. It depends on how it depends. However, there is no difference that the above relationship is expressed by a linear function relationship.

  The above-described module coefficient M and circuit gain B actually have only a finite value. Therefore, as is apparent from FIG. 5, the temperature Tx of the crystal unit 3 cannot be set to a constant value as long as the set temperature Tr is set to a certain fixed value as in the prior art. When the difference (Tr-Tout) in the outside air temperature Tout is large, that is, when the outside air temperature Tout is low, the temperature of the crystal unit 3 is always lowered. This is an essential problem that the temperature of the crystal unit 3 cannot be made constant in the conventional OCXO.

<Principle of the present invention>
As a result of the considerations related to the prior art as described above, as long as the set temperature Tr is set to a certain fixed value, it is concluded that the temperature Tx of the crystal unit 3 cannot be a constant value, and the heat energy supplied to the heat source 1 is the heat source. When the temperature difference (Tr-Tout) between the set temperature Tr and the outside air temperature Tout is large, that is, when the outside air temperature Tout is low, the target temperature of the crystal unit 1 is obtained. It came to mind that the set temperature Tr itself can be changed by the outside temperature Tout.

  That is, at a certain outside air temperature Tout, the temperature difference (Tr−Tic) between the set temperature Tr and the measured temperature Tic of the temperature sensor 2 is monitored, and the temperature difference (Tr−Tic) is multiplied by a predetermined feedback coefficient. The feedback amount δT is fed back and added to the target temperature Ttarg which is the final temperature of the crystal resonator 3 to construct a feedback system for generating a new set value Tr. With this feedback system, the temperature Tx of the crystal unit 3 can be converged to the target temperature Ttarg, which is a fixed value set as an initial set value. That is, by changing the set temperature Tr as described above, as shown in FIG. 6, even if the measured temperature Tic, which is the circuit temperature of the module based on the outside air temperature, changes, the temperature Tx of the crystal unit 3 has a slope of zero. The characteristics can be That is, even if the temperature difference (Tr−Tout) between the set temperature Tr and the outside air temperature Tout changes, the temperature Tx of the crystal unit 3 can be held at the target value Ttarg that is a constant value. Therefore, even if the temperature difference (Tr−Tout) between the set temperature Tr and the outside air temperature Tout changes, the temperature of the crystal unit 3 can be set as the target temperature Ttarg, and the oscillation frequency can be kept constant with high accuracy. Can do.

The present invention based on the above principle is characterized by the following points.
1) The measured temperature based on the outside temperature measured by the temperature sensor is compared with the set temperature. The temperature is stored in a thermostatic chamber that is controlled so that the difference between the two is reduced. Is a thermostatic bath electronic device having a control system for controlling the temperature of the device that changes to a target temperature that is a predetermined fixed value,
The control system is configured such that the target temperature is a fixed value so that the set temperature increases when the measured temperature decreases, and the set temperature decreases when the measured temperature increases. Adding a predetermined feedback amount (δT) to the temperature (Ttarg) to generate a new set temperature for comparison with the measured temperature.

2) In the above 1), the control system is
The control system is
A comparator that compares the measured temperature signal representing the measured temperature with the set temperature signal representing the set temperature and sends a temperature difference signal representing the temperature difference between the two;
Control means for controlling the calorific value of the heat source housed in the thermostatic chamber based on the temperature difference signal;
A feedback system having a feedback constant setting unit that generates a feedback amount signal representing the feedback amount based on the temperature difference signal;
An adder that adds the target temperature signal representing the target temperature set in the temperature setting unit and the feedback amount signal to generate the set temperature signal and that is used as one input of the comparator;
A temperature sensor that measures the temperature based on the outside air temperature, generates the measured temperature signal, and uses the other input of the comparator;
Having

3) In 2) above, the change in the feedback signal in the feedback system, which is an electrical feedback path, follows the change in the measured temperature signal based on the temperature feedback path from the heat source to the temperature sensor with a delay. The phase compensation means is provided in the feedback system.

4) In 2) or 3) above, the thermal resistance between the heat source and the outside of the thermostat is Θho, the thermal resistance between the temperature sensor and the outside of the thermostat is Θco, and the heat source and the temperature The thermal resistance between the sensor and Θhc is defined as (Θho · Θco) / (Θhc + Θco) as a module coefficient Mic, and B = a gain of heat with respect to the temperature difference, α = 1 / (1 + Mic · B), Fb = When the gain of the feedback system is used, the relationship is {−1 <(B · α · Fb) <1}.

5) In any one of the above 2) to 4), the heat source is formed by a heater, and the control means controls a current supplied to the heater.
The amount of feedback is generated based on the current supplied to the heater or the power consumed by the heater.

6) In any one of the above 2) to 4), the feedback amount is generated based on an output of the comparator that has directly fed back to the feedback system.

7) In the above 6), clamping means is provided in the feedback system so that the feedback amount (δT) ≧ 0.

8) In any one of 1) to 7) above, the device is a crystal resonator.

  In the present invention, a new set value is generated by adding a predetermined feedback amount to a target temperature that is a fixed value, and the new set value is compared with the actually measured temperature so that the temperature difference between the two becomes small. Since the temperature inside is controlled, the temperature difference of the device stored in the thermostat can be kept constant with the temperature difference being zero. As a result, the temperature characteristics of the device can be easily made constant even when the outside air temperature fluctuates, and stable operation over a long period of time can be ensured. In particular, when the device is a crystal resonator, an oscillation signal with a high-accuracy frequency can be continuously generated stably.

It is a block diagram which shows the thermostat crystal oscillation apparatus which concerns on 1st Embodiment of this invention. It is a block diagram which shows the thermostat type crystal oscillation apparatus which concerns on 2nd Embodiment of this invention. It is a schematic diagram explaining the relationship between the flow of the thermal energy in OCXO and the temperature of each part. FIG. 6 is a characteristic diagram showing a relationship between a module coefficient M and a temperature T. It is a characteristic view which shows the relationship of each part temperature with respect to the difference of preset temperature and external temperature in OCXO which concerns on a prior art. It is a characteristic view which shows the relationship of each part temperature with respect to the difference of preset temperature and external temperature in OCXO which concerns on this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Here, in each embodiment, the same number is attached | subjected to the same part, and the overlapping description is abbreviate | omitted.

  Note that each embodiment described below is merely an example, and there is no intention of excluding various modifications and technical applications that are not explicitly described in the following embodiment. Each configuration of the following embodiments can be modified and implemented without departing from the spirit of the embodiments, can be selected as necessary, or can be appropriately combined.

<First Embodiment>
FIG. 1 is a block diagram showing a thermostatic chamber type crystal oscillator (OCXO) according to a first embodiment of the present invention. As shown in the figure, the thermostat 100 houses a crystal resonator 3 driven by an oscillation circuit 12 together with a control system 101 for controlling the internal temperature of the thermostat 100 at a constant level. Here, the crystal unit 3 is a device affected by the outside air temperature (environment temperature) Tout.

  The control system 101 compares the measured temperature signal V_Tic representing the measured temperature Tic based on the outside air temperature Tout detected by the temperature sensor 2 with the set temperature signal V_Tr representing the set temperature Tr by the comparator 8, and the temperature difference (Tr The amount of heat generated by the heater (heat source) 1 is controlled via the transistor (control means) 10 so that the temperature difference signal V_ (Tr-Tic) representing -Tic) becomes small. Here, the control system 101 according to the present embodiment is configured such that when the measured temperature Tic is lowered, that is, when the outside air temperature Tout is lowered, the target temperature signal V_Ttarg representing the target temperature Ttarg so that the set temperature Tr becomes higher. Is added with a feedback amount signal V_δT representing a predetermined feedback amount δT by the adder 6 to generate a new set temperature signal V_Tr to be compared with the actually measured temperature signal V_Tic.

  On the other hand, when the measured temperature Tic is rising, that is, when the outside air temperature Tout is rising, the adder 6 adds a predetermined feedback amount signal V_δT to the target temperature signal V_Ttarg so that the set temperature Tr becomes low. Then, a new set temperature signal V_Tr to be compared with the actually measured temperature signal V_Tic is generated.

  Here, the target temperature Ttarg is a target temperature in the thermostat 100, that is, a target temperature of the crystal unit 3, and is set in the temperature setting unit 5 as a fixed value.

  A new set temperature signal V_Tr generated by adding the feedback amount signal V_δT to the target temperature signal V_Ttarg is one input of the comparator 8. A measured temperature signal V_Tic is supplied to the other input of the comparator 8. Thus, the comparator 8 outputs the temperature difference signal V_ (TR−Tic) generated by comparing the new set temperature signal V_Tr and the actually measured temperature signal V_Tic.

  The temperature difference signal V_ (TR−Tic) is multiplied by a predetermined circuit gain by the circuit gain setting unit 9 and supplied to the gate of the transistor (control means) 10. Here, the circuit gain set in the circuit gain setting unit 9 is the gain B of the circuit system formed by the comparator 8, the circuit gain setting unit 9, the transistor 10, and the heater 1. 1 for converting the electric power to be consumed by the electric power.

  Thus, a current corresponding to the temperature difference signal V_ (TR−Tic) flows through the heater (heat source) 1 to generate a predetermined amount of heat to heat the interior of the thermostatic chamber 100.

  The feedback system 102 in this embodiment includes a temperature difference detection unit 11, a phase compensation unit 13, and a feedback constant setting unit 7. Here, since the temperature difference detection unit 11 can consider that the electric power consumed by the heater 1 is the amount of heat leaked by the heat leak 200 from the thermostat 100 to the outside air 4, the temperature difference (Tr-Tic) The temperature difference signal V_ (Tr-Tic) representing the temperature difference (Tr-Tic) is generated by detecting the amount of electric power or current consumed to reduce the voltage and fed back. The temperature difference signal V_ (Tr−Tic) of the feedback system 102 is subjected to a predetermined phase compensation (delay processing) by the phase compensation unit 13 and then multiplied by a predetermined feedback constant by the feedback constant setting unit 7. V_δT is supplied to the adder 6. Here, the feedback coefficient set in the feedback constant setting unit 7 is for adjusting the feedback constant Fb of the feedback system 102 to be a predetermined value.

Here, the phase compensation unit 13 ensures the realization of predetermined feedback control in the feedback system 102 by the following function. That is, the change in the feedback signal in the feedback system 102 which is an electrical feedback path is generally faster than the change in the actually measured temperature signal based on the temperature feedback path 201 from the heater (heat source) 1 to the temperature sensor 2. Therefore, in this state, there is a possibility that the output of the comparator 8 that compares the two and outputs the temperature difference oscillates. Therefore, in order to reliably avoid such an oscillation phenomenon, in this embodiment, the electrical change of the feedback signal in the feedback system 102 follows the change of the measured temperature signal based on the temperature feedback path 201 with a delay. A phase compensation unit 13 is provided. Oscillation phenomenon at the output of the comparator 8 can be reliably avoided by the predetermined phase compensation in the phase compensation unit 13.

  The normal OCXO includes a heater 1 for heating, and the temperature of the thermostatic bath 100 is controlled by a balance between heating by the heater 1 and natural cooling due to leakage from the thermostatic bath 100 to the outside air 4. That is, it is normal that no positive cooling means such as a cooler is provided. Therefore, when the outside air temperature Tout becomes very high and the actually measured temperature Tic by the temperature sensor 2 becomes larger than the set temperature Tr, in this embodiment, the current of the heater 1 becomes zero and the heating is stopped. From there, there is no cooler function even if the outside temperature Tout further rises, so that the measured temperature Tic also rises almost following the outside temperature Tout.

  In this embodiment in which the detection of the outside temperature Tout is monitored by the current supplied to the heater 1 or the power consumed by the heater 1, the current (power) supplied to the heater 1 when Tic> Tr is satisfied. ) Is fixed at zero, so it is necessarily fixed at Tr = Ttarg. That is, it cannot be avoided that the temperature of the entire control system 101 cannot be controlled due to the lack of the cooling function and rises simultaneously with the outside air temperature Tout. However, in the present embodiment, when the outside air temperature Tout drops below the target temperature Ttarg, the temperature control regarding the predetermined thermostat 100 is started immediately, and the function of maintaining a constant temperature is restored.

  In the OCXO according to the present embodiment as described above, the set value Tr that is one input of the comparator 8 is made variable based on the feedback amount δT obtained by the feedback system 102. That is, a predetermined feedback amount δT is added to the target temperature Ttarg which is a fixed value by the adder 6 to generate a new set value Tr, and the new set value Tr and the measured temperature Tic are compared by the comparator 8. The temperature in the thermostatic bath 100 is controlled so that the temperature difference (Tr-Tic) becomes smaller. As a result, as shown in FIG. 6, the temperature of the crystal unit 3 housed in the thermostat 100 can be kept constant with the temperature difference (Tr-Tic) being zero. Thus, even if the outside air temperature 4 varies, the temperature characteristics of the crystal unit 3 can be easily made constant, and the oscillation operation of the crystal unit 1 at a stable constant frequency over a long period can be ensured. .

As described above, the feedback amount δT of the feedback system 102 needs to converge to a constant value without diverging in order to constantly exhibit the operation and effect of the present embodiment. The convergence condition is that the relationship of the expression {−1 <(B · α · Fb) <1} is established in the circuit including the feedback system 102.
Here, the thermal resistance between the heater (heat source) 1 and the outside of the thermostat 100 (outside air 4) is Θho, and the thermal resistance between the temperature sensor 2 and the outside of the thermostat 100 (outside air 4) is Θco, the heater. The thermal resistance between the (heat source) 1 and the temperature sensor 2 is defined as Θhc, and (Θho · Θco) / (Θhc + Θco) is defined as a module coefficient Mic, and B = circuit gain, α = 1 / (1 + Mic · B) To do.

<Examination of convergence conditions>
The convergence condition was derived from the following considerations.
In this embodiment, at a certain outside air temperature Tout, a temperature difference (Tr−Tic) between the set temperature Tr and the actually measured temperature Tic measured by the temperature sensor 2 is detected by the comparator 8 and the temperature difference (Tr−Tic). The feedback constant setting unit 7 multiplies the signal by a predetermined feedback coefficient to generate a feedback amount δT. At this time, the proportional relationship of the following equation is established from Equation (6).
Tr-Tic = α ・ (Tr-Tout)
However, α = 1 / (1 + Mic ・ B)

At this time, the amount of heat generated by the heat source 1 is calculated from the equation (5).
P = B ・ (Tr-Tic)
Therefore, the temperature difference between the set temperature Tr and the actually measured temperature Tic can be actually detected by the measured value of the power of the heat source 1 or the like.

Therefore, formula (6) is substituted into formula (5) and the formula is modified as follows.
P = B ・ α ・ (Tr-Tout)

  Next, consider that a feedback system 102 that updates a set temperature Tr each time by multiplying a certain initial value, P (0), Ttarg by a certain feedback coefficient, is repeated n times.

  A condition for preventing the set temperature Tr from divergence when such a feedback operation is added will be described using a series with an initial value when there is no feedback operation. Here, the amount of heat generated when there is no feedback operation is P (0), the set temperature Tr at that time is set as T = Ttarget, and a constant feedback coefficient is multiplied from the initial value to update the set value Tr every time n times. Let us first consider the repetition, and then find the limit where n is infinite.

Here, the target temperature Ttarg is a certain fixed value.
P (0) = B ・ α ・ (Ttarg-Tout)
Tr (1) = Ttarg + Fb ・ P (0)
P (1) = B ・ α ・ (Tr (1)-Tout)
= B ・ α ・ (Ttarg + Fb ・ P (0)-Tout)
= B ・ α ・ (Ttarg-Tout) + B ・ α ・ Fb ・ P (0)
= (1 + B ・ α ・ Fb) ・ P (0)
Tr (2) = Ttarg + Fb ・ P (1)
= Ttarg + Fb ・ (1 + B ・ α ・ Fb) ・ P (0)
P (2) = B ・ α ・ (Tr (2)-Tout)
= B ・ α ・ (Ttarg + Fb ・ (1 + B ・ α ・ Fb) ・ P (0)-Tout)
= B ・ α ・ (Ttarg-Tout) + B ・ α ・ Fb ・ (1 + B ・ α ・ Fb) ・ P (0)
= {1 + B ・ α ・ Fb + (B ・ α ・ Fb) ² } ・ P (0)
Tr (3) = Ttarg + Fb ・ P (2)
= Ttarg + Fb ・ {1 + B ・ α ・ Fb + (B ・ α ・ Fb) ² } ・ P (0)
P (3) = B ・ α ・ (Tr (3)-Tout)
= B ・ α ・ [Ttarg + Fb ・ {1 + B ・ α ・ Fb + (B ・ α ・ Fb) ² } ・ P (0)-Tout]
= B ・ α ・ (Ttarg-Tout) + B ・ α ・ Fb ・ {1 + B ・ α ・ Fb + (B ・ α ・ Fb) ² }
・ P (0)
= {1 + B ・ α ・ Fb + (B ・ α ・ Fb) ² + (B ・ α ・ Fb) ³ } ・ P (0)
...
P (n) = {1 + B · α · Fb + (B · α · Fb) ² + (B · α · Fb) ³ + ... + (B · α · Fb) ⁿ } · P (0)

  That is, the amount of heat P (n) after repeating the feedback operation n times is a geometric series multiple of the initial value P (0) with the above (B · α · Fb) as a common ratio.

Therefore, the convergence condition after repeating infinite feedback is
| (B ・ α ・ Fb) | <1
However, α = 1 / (1 + Mic ・ B)
It is.

Under the convergence condition, P (∞) and Tr (∞) represented by an infinite series converge to the following values.
P (∞) = {1 / (1-B ・ α ・ Fb)} ・ P (0)
Tr (∞) = Ttarg + {Fb / (1-B ・ α ・ Fb)} ・ P (0)
Where α = 1 / (1 + Mic ・ B), P (0) = B ・ α ・ (Ttarg-Tout), and
{Fb / (1−B · α · Fb)} · P (0) is the feedback amount δT.

Furthermore, from the equation (9), the temperature Tx of the crystal unit 3 is given by the following equation.
Tx (∞) =-{1 + B ・ (Mic-Mx)} ・ {1 / (1 + Mic ・ B)} ・ (Tr (∞)-Tout) + Tr (∞) = {1 + B ・ ( Mic-Mx)} ・ {1 / (1 + Mic ・ B)} ・ Tout + B ・ (Mic-Mx) ・ {1 / (1 +
Mic ・ B)} ・ Tr (∞)
= {1 + B ・ (Mic-Mx)} ・ {1 / (1 + Mic ・ B)} ・ Tout + B ・ (Mic-Mx) ・ {1 / (1 +
Mic ・ B)} ・ [Ttarg + {Fb / (1-B ・ α ・ Fb)} ・ P (0)]
= {1 + B ・ (Mic-Mx)} ・ {1 / (1 + Mic ・ B)} ・ Tout + B ・ (Mic-Mx) ・ {1 / (1 +
Mic ・ B)} ・ [Ttarg + {Fb / (1-B ・ α ・ Fb)} ・ B ・ α ・ (Ttarg-Tout)]
= [{1 + B ・ (Mic-Mx)} ・ {1 / (1 + Mic ・ B)}-B ・ (Mic-Mx) ・ {1 / (1 + Mic
・ B)} ・ {Fb / (1-B ・ α ・ Fb)} ・ B ・ α] ・ Tout + B ・ (Mic-Mx) ・ {1 / (1
+ Mic ・ B)} ・ {1 + Fb / (1-B ・ α ・ Fb)} ・ B ・ α ・ Ttarg ・ ・ ・ （10）
It becomes.

  The condition that the temperature Tx of the crystal unit 3 is constant regardless of the outside air temperature Tout is that the differential coefficient related to the outside air temperature Tout in the above equation (10) is zero.

That is, if the circuit gain B and the feedback coefficient Fb are adjusted so that the relationship of the following equation is established, the temperature Tx of the crystal unit 3 becomes constant regardless of the outside air temperature Tout.
[{1 + B ・ (Mic-Mx)} ・ {1 / (1 + Mic ・ B)}-B ・ (Mic-Mx) ・ {1 / (1 + Mic ・ B)} ・ {Fb / (1 -B ・ α ・ Fb)} ・ B ・ α] = 0

Second Embodiment
FIG. 2 is a block diagram showing a thermostatic chamber type crystal oscillator according to a second embodiment of the present invention. As shown in the figure, the feedback system 104 in this embodiment is configured to directly feed back the temperature difference signal V_ (Tr−Tic) that is the output of the comparator 8. That is, the feedback amount signal V_δT is generated based on the output of the comparator 8 fed back to the feedback system 104 directly.

  Further, the feedback system 104 in the present embodiment is provided with a clamp circuit 14 together with the phase compensator 13 having the same function as in the first embodiment. The clamp circuit 14 clamps the value to zero or more so that the temperature difference signal V_ (Tr−Tic) does not become negative so that the feedback amount (δT) ≧ 0.

  In this embodiment as well, as in the first embodiment, the temperature of the crystal unit 3 housed in the thermostat 100 can be kept constant with the temperature difference (Tr-Tic) being zero (see FIG. 6). . However, in the present embodiment, the clamp circuit 14 is necessary for the following reason.

  In the first embodiment, even when there is no cooler, the current (electric power) supplied to the heater 1 is fixed to zero when Tic> Tr is satisfied, so that eventually, Tr = Ttarg Fixed to. On the other hand, in the control system 104 in which the outside air temperature Tout is detected by the output of the comparator 8 of the actually measured temperature Tic and the set temperature Tr by the temperature sensor 2 as in this embodiment, the outside air temperature Tout increases and Tic> Tr Even in this case, the comparator 8 continuously outputs the negative temperature difference signal V_ (Tr-Tic) corresponding to the temperature difference (Tr-Tic). The value Tr continues to be controlled to a value lower than the target temperature Ttarg.

  However, since OCXO does not have a cooler function, the measured temperature Tic rises following the outside air temperature Tout. In this embodiment, the set value Tr is not fixed at the target temperature Ttarg and is set to a very low value. Will be.

  Therefore, once the set temperature Tr is set to a very low value, even if the outside air temperature decreases, the heating by the heater 1 does not start until the set very low set temperature Tr is reached. There arises a problem that the amount of undershoot of the temperature of the entire system becomes much larger than when the current (electric power) supplied to 1 is used for sensing the outside temperature Tout.

  Therefore, when Tr = Ttarg + δT (Ttarg is a fixed initial set value and δT is the feedback amount), when controlling the set temperature Tr, the normal function that has a heater function but does not have an active cooling function In OCXO, the circuit should be configured so that the feedback amount δT ≧ 0.

<Other embodiments>
In the above embodiment, the case where the device influenced by the outside air temperature (environment temperature) Tout is taken as an example of the crystal unit 3 and OCXO is used as the thermostatic bath electronic device has been described, but of course it is not limited to OCXO. The present invention can be applied without any special restriction when it is desired to keep the temperature of a device stored in the thermostat 100 constant, that is, when a device whose characteristics change depending on the outside air temperature Tout is stored. In this case, the characteristics of the housed device can be stabilized.

  For example, another example of this type of device is a piezoelectric sensor. This is because the detection accuracy of the piezoelectric sensor also depends on the outside air temperature.

DESCRIPTION OF SYMBOLS 1 Heat source 2 Temperature sensor 3 Crystal oscillator 4 Outside air 5 Temperature setting part 6 Adder 7 Feedback constant setting part 8 Comparator
DESCRIPTION OF SYMBOLS 10 Transistor 11 Temperature difference detection part 12 Oscillation circuit 13 Phase compensation part 14 Clamp circuit 100 Thermostatic chamber 101, 103 Control system 102, 104 Feedback system

Claims (8)

The measured temperature based on the outside air temperature measured by the temperature sensor is compared with the set temperature. The temperature is stored in a thermostatic chamber that is controlled so that the difference between the two is small. A thermostatic bath electronic device having a control system for controlling the temperature of the device to be a target temperature that is a predetermined fixed value,
The control system is configured such that the target temperature is a fixed value so that the set temperature increases when the measured temperature decreases, and the set temperature decreases when the measured temperature increases. A constant-temperature bath type electronic apparatus, wherein a predetermined set point is added to the temperature to generate a new set temperature for comparison with the measured temperature. The control system is
A comparator that compares the measured temperature signal representing the measured temperature with the set temperature signal representing the set temperature and sends a temperature difference signal representing the temperature difference between the two;
Control means for controlling the calorific value of the heat source housed in the thermostatic chamber based on the temperature difference signal;
A feedback system having a feedback constant setting unit that generates a feedback amount signal representing the feedback amount based on the temperature difference signal;
An adder that adds the target temperature signal representing the target temperature set in the temperature setting unit and the feedback amount signal to generate the set temperature signal and that is used as one input of the comparator;
A temperature sensor that measures the temperature based on the outside air temperature, generates the measured temperature signal, and uses the other input of the comparator;
The thermostat-type electronic device according to claim 1, characterized by comprising:   The feedback system is phased so that the change in the feedback signal in the feedback system, which is an electrical feedback path, follows the delay with respect to the change in the measured temperature signal based on the temperature feedback path from the heat source to the temperature sensor. The thermostat-type electronic device according to claim 2, further comprising compensation means.   The thermal resistance between the heat source and the outside of the thermostat is Θho, the thermal resistance between the temperature sensor and the outside of the thermostat is Θco, and the thermal resistance between the heat source and the temperature sensor is Θhc. When (Θho · Θco) / (Θhc + Θco) is defined as a module coefficient Mic, and B = a gain of heat with respect to the temperature difference, α = 1 / (1 + Mic · B), and Fb = a gain of the feedback system, { The thermostatic bath electronic device according to claim 2 or 3, wherein -1 <(B · α · Fb) <1}. The heat source is formed by a heater, and the control means controls a current supplied to the heater.
5. The thermostatic bath electronic device according to claim 2, wherein the feedback amount is generated based on a current supplied to the heater or an electric power consumed by the heater.   5. The thermostatic bath electronic device according to claim 2, wherein the feedback amount is generated based on an output of the comparator that has directly returned to the feedback system. 6.   7. The thermostat-type electronic device according to claim 6, wherein clamping means is provided in the feedback system so that the feedback amount (δT) ≧ 0.   The thermostatic electronic device according to any one of claims 1 to 7, wherein the device is a crystal resonator.

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